It is now understood that periodic behaviour is not confined to a limited number of physiological processes but is abundant in most biological systems. Periodicity in processes of the human body encompass phenomena such as genetic interactions, heartbeat rhythms, oscillating secretory, retina and muscle cells, cytoskeletal structures, bacterial oscillations, rhythmic oscillations (1-3). In 1952, whilst modelling neurons, Hodgkin and Huxley were able to accurately model the action potential in the giant squid axon (4). Their nonlinear ordinary differential equations approximate electrical characteristics of excitable oscillatory cells such as cardiomyocytes and neurons.
A number of research groups are now able to grow neurons on chips using a variety of techniques including an aligned micro-contact printing technique, patch clamping (which yields very accurate information but is invasive) and extracellular recordings by means of external micro-transducers or optical measurements (which are non-invasive) (5, 6), and it has recently been shown that Parkin diseased neurons can also be grown on a chip (7). In 2012 (8), it was shown that citicoline may be beneficial as a protective treatment against Alzheimer's following a stroke.
It is amongst the objects of the present invention to provide cell based assays which allow cells to be tested for an electrophysiological response to various stimuli. Such assays may be used in the testing of agents which may be of use in treating disease.